What Is Bread Mold?

What Is Bread Mold?

Bread mold is a type of fungus that likes to grow on bread because it is often warm and moist. Bread mold needs warmth and moisture, along with oxygen, to thrive. Bread provides an ideal substrate (or living surface) for various types of molds.

Bread Mold Facts

Believe it or not, bread mold is actually a type of plant. Molds grow much faster than traditional plants, due mostly to the fact that their reproductive parts float around in the air, constantly looking for a place to land and thrive. It just so happens that bread, with its warmth and moisture, is the perfect substrate for mold to grow on.

When bread mold spores find a warm and moist surface, they attach and start to reproduce and grow very rapidly. This spreading of spores further infects bread (if bread is the substrate) and sends even more spores into the air.

What Is Bread Mold?

Each bread mold spore has two parts–one is long and black and the other is short and is capable of breaking into the bread to absorb food and moisture.

Mold doesn’t just grow on bread–it can also grow on anything moist and warm, like meat, shoes and clothes, even things that incidentally wet like books or a tile floor.

There are many different types of mold in all different shapes and sizes. They have names like Aspergillus, Monascus, Rhizopus, Penicillium, and Fusarium. Each of these species has its own unique color and apperance–Rhizopus is black and fuzzy, while Aspergillus is small and hard to see. The Penicillium species is more of a dark green color with a white border.

Harmful Effects of Bread Mold

When human beings come into close contact with mold of any type, they run the risk of absorbing mycotoxins through the skin, mucous membranes, and airways. These mycotoxins are produced naturally by any mold, but especially the mold that makes bread mold. Mycotoxings are very dangerous to human life, as once they attach to the inside of our bodies, they can easily spread and infect the entire body and immune system. Mycotoxins can create all sorts of health problems, from simple allergies and contact hypersensitivity, to more severe respiratory problems like asthma, and chronic coughing, and grave health conditions like permanent memory loss, depression, anxiety, reproductive system failure, sometimes even death.

Benefits of Bread Mold

Some molds that grow on bread are beneficial in the production of foods. Mold on cheeses, sausages, breads, and soy sauce (as well as alcohol like sherries and wines) actually add to the taste of many of these products.

When combined with special foods and a healthy lifestyle, cultured mold can be used to reduce cholesterol.

Bread molds are used in the production of some beneficial drugs.Most famously, the Penicillium chrysogenum mold is used to produce the life-saving antibiotic we call penicillin.

Other molds and bread molds are used to create other life-saving drugs, namely Aspergillus terreus which is used to create cholesterol-lowering drugs, and Tolypocladium Infatum which is used to combat the rejection of transplanted organs.

Bread Mold Growth

The growth of bread mold depends on many different factors, with temperature and moisture being the most important two. At lower temperatures, mold is able to grow, but it grows at a much slower rate. Most molds on planet Earth thrive in temperatures higher than 70°–this is why we refrigerate food. The average fridge temperature is between 39 and 41 degrees, seriously limiting the growth rate of molds.

Very cold temperatures, such as those found in an average freezer, will stop the mold of growth completely. Freezing temperatures kill molds and inhibit their growth.

Remember that bread mold is a living plant organism, one that needs both moisture and oxygen to grow. Moisture is absorbed by the mold plant itself, causing the plant to grow faster just like when you water a plant in your garden.

Bread Mold Science Fair Project

A popular bread mold based science fair project is to determine if mold grows faster at higher or lower temperatures. It’s a popular topic because it is easy to prove with a simple science experiment. Here’s how you perform this classic bread mold science fair project.


  1. 15 slices of sandwich bread. This bread is used because it is inexpensive and each slice will be the same size, weight, and thickness.
  2. 15 sealable sandwich bags.
  3. 1 piece of film or clear plastic with a 10x10cm grid drawn onto it.
  4. Q-Tip
  5. Clean Knife
  6. Chopping board
  7. Sticky notes
  8. Marker pen
  9. Mold Spores. You can sometimes acquire these from science catalogs or other educational resources. There are plenty of mold spores in the air that will eventually grow on your bread, but getting mold spores and applying them yourself will take less time.
  10. Mask
  11. Gloves


Label your bags with sticky notes. Mark 5 bags as ‘A’, 5 as ‘B’ and 5 as ‘C’.

Cut your bread into 10 x 10 squares.

After you place mold spores on the bread, put one slice into each bag and seal them tightly.

Place all of the ‘A’ bags into the freezer, the ‘B’ bags into the refrigerator and the ‘C’ bags in a warm room. Because the bags in the freezer and fridge will not be getting much light it is best to cover the ‘C’ bags as well so that the light difference doesn’t affect the outcome.

At the same time each day, count the number of square centimeters of mold on each slice of bread. Never open the bags.

Repeat this process for 10 days or until there are measurable results.

Keep careful notes on your results for every slice of bread for the duration of the experiment. You can even take pictures or draw the bread pieces. Now average the results for each sample type, A, B, and C.

You can plot the mold coverage on a graph and determine your results. Plot the amount of mold on each piece of bread and compare it to the number of days. Do this with a sheet of graph paper and colored pens or on a computer graph program.